a minimum of tension just to approximate the edges, taking care in avoiding cutting through the friable liver tissue. Applica- tions of deep suture bites are likewise avoided to prevent necrosis of normal liver tissue.
The alternative suture would be an absorbable suture like polyglactin.
Bowel Anastomosis
Leakage of intestinal contents or its frank breakdown after a bowel anastomosis carries severe consequences. A critical factor that determines anastomotic integrity is the application of proper suturing technique and material. However, it must be empha- sized that half of the procedure is accomplished before the actual resection and anastomosis, i.e., during the preparation of the segments that are to be resected and the bowel ends that are to be joined together.
Another unique feature of the procedure is that of tissue inversion. The repair is reinforced by the proper approximation and healing of the seromuscular layer of each bowel end. Inversion therefore provides a serosa-to-serosa apposition over a mucosa-submucosal repair.
All the layers of the bowel wall are characteristically soft with minimal to moderate dense fibrous support. As such it is easy to penetrate. Using taper point or round point needles is appropri- ate. Anything sharper than a taper or round needle may be more traumatic or more risky than is desirable. Moreover, the depth of the bite in bowel anastomosis need not be very deep and the working space inside the abdominal cavity may be somewhat confined. A 1/2 circle needle is standard for this repair. Bowels are lumenous structures with fluid and gaseous contents and its repair is ideally done without tension which seldom offers resistance. Therefore, the diameter of the needle must be thin to keep it water-tight but at the same time relatively strong and stable given the necessary thin wire diameter. The average thickness of bowel walls that are to be anastomosed only require medium chord length. And in order to create the least puncture injury to the bowel walls, atraumatic needles, i.e., those with a swage attachment rather than eyed, are desirable.
Healing time is relatively fast with the anastomosis assuming tensile strength in about 7-14 days. The serosal layer heals faster than the submucosa but it is the latter, being the most fibrous among the 4 layers that gives the anastomosis its required strength. The submucosal repair therefore, is the most important for the surgeon. Consequently, the suture material that is ideal for bowel anastomosis must therefore retain tensile strength beyond the healing time of the slowest healing tissue - the submucosa. Absorbable suture materials are commonly used but non-absorbables are also popular particularly among single layer technique of repair.
It is not uncommon for the prolonged presence of a suture in the mucosa to provoke significant foreign body reaction and granuloma formation. This has great significance in the gastric mucosa as it may lead to post-operative anastomotic ulcer formation. Hence, for the inner layer in gastric or duodenal anastomosis, short term absorbable suture materials are pre- ferred. A popular compromise in single layer closure technique is a longer term absorbable suture material such as polyglactin, polyglycolic and polydioxanone.
In a double layer anastomosis, non-absorbables are com- monly used in the seromuscular inverting stitch while virtually any absorbable material like poliglecaprone is acceptable in the mucosal and submucosal layers. The rationale here is the required prolonged reinforcement of the seromuscular repair for the slower healing submucosal layer and for the quickly ab- sorbed inner suture.
There are, however, suturing techniques that accomplish bowel anastomosis using single layer repair. These are mostly applied in esophageal and rectal anastomoses where the procedures are performed in very limited and confined spaces and where the margins of resection are too short to adequately permit an inversion technique. The anastomoses in such cases may be commonly performed with a running stitch, although an interrupted technique is also popular for facilitating a precise re- approximation. Here, both braided and monofilament materials are utilized depending on the technique, i.e., monofilament for running, continuous stitch and braided for interrupted. Keep in
mind that a continuous non-absorbable suture would, in essence, serve as a purse-string that would permanently limit the size of the lumen as opposed to employing the interrupted technique using absorbables.
In considering the size of the suture material, there has to be a reasonable balance between the required tensile strength and tissue reaction due to the foreign body. Suture material strength is a function of the size. But bowel anastomosis is best done without tension. The bowel walls are neither thick nor fibrous where stress and strain to suture material is minimal. But if the suture is too “fine,” there is always the possibility of “cutting through” the tissues with the slightest strain. Therefore, 3-0 is the standard while 2-0 is acceptable as well as 4-0.
Finally, a material that elicits the least amount of tissue reaction is desirable in order to minimize incidence of adhesions between the site of repair and other peritoneal surfaces as well as to eliminate granuloma formation within and without the bowel.
Vascular Anastomosis and Repair
Vascular suturing has specific demands different from other suturing techniques. Suturing and repair of vessels demand precision in the approximation of the cut edges to maintain integrity of the lumen and prevent dehiscence/breakdown which has more disastrous consequences. Tensile strength retention and absorption rate are very critical in determining the choice of suture. Blood vessels are subjected to a tremendous amount of pressure per square millimeter and for this reason, sutures have to be strong and absorbed/broken down only after a long time. Given also the special situation of anastomosing blood vessels to synthetic grafts, one must remember that only one side of the repair will undergo biologic wound healing and repair. It has also been noted that using absorbable sutures or sutures that are easily broken down (including silk), leads to a higher incidence of vascular anastomotic breakdown or pseudo-aneurysm formation. The ideal suture for this situation is a suture that is inert, non- traumatic, will retain its tensile strength for a long time and will not easily be broken down or absorbed. Polypropylene has been found to conform to most of these requirements. It is monofila-
ment, non- absorbable and incites very minimal inflammatory reaction. This is best used with a 1/2 circle, tapered BV-1 or RB- 1 needle.
Vessels may be sutured in a running, continuous fashion, for which a double-armed suture is best or in an interrupted manner, especially for smaller vessels. Continuous suture technique for very small vessels may have a purse-string effect which may narrow the lumen further.
An alternate suture for use in vascular surgery is braided polyester.
Application of Retention Sutures
These are utilized as reinforcing sutures to relieve pressure on the suture line and to prevent postoperative wound disrup- tion in abdominal wound closures in particularly vulner- able patients, as in the elderly and immunocompromised patients.
Retention sutures utilize strong and large suture materials, in particular, non-absorbable sutures. Absorbable sutures need not be used as these sutures will eventually be removed in a couple of weeks. Sutures that may be used for this particular procedure include nylon, polypropylene or silk 2, 1 or 0. Even stainless steel or wire may be used. These same suture materials may be used even in the presence of infection as they produce the least inflammatory reaction. The best needle to use would be a large cutting-edge needle, so as to penetrate the layers of the abdomi- nal wall with ease. Retention sutures should be applied prior to closing any layer of the abdominal wall and must be applied under direct vision to prevent bowel injury. After all retention sutures have been applied and after all the layers of the ab- dominal wall have been closed, they are all individually tied. To prevent tying the retention sutures too tightly, rubber bridges are applied. These rubber bridges may be in the form of cut strips of drainage tubes or catheters.
REFERENCES
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Feliciano DV, Moore EE and Mattox KL. TRAUMA, 3rd ed., Stamford, Conn,: Appleton & Lange, 1996
Rout WR. Gastrointestinal Suturing. In: Zuidema GD, Ritchie WP, Jr. (eds), Shackelford’s Surgery of the Alimentary Tract, 4th ed., Philadelphia, PA: WB Saunders; 1996
Rout WR. Closure of Wound. In: Zuidema GD, Ritchie WP, Jr. (eds), Shackelford’s Surgery of the Alimentary Tract, 4th ed., Philadelphia, PA: WB Saunders; 1996 Rutherford RB. Atlas of Vascular Surgery: Basic Techniques and Exposures; WB Saunders Co., 1993
Singer AJ, Hollander JE and Quinn JV. Evaluation and Management of Traumatic Lacerations; The New England Journal of Medicine, 1997, 337:1142-1148 Wilson RF and Walt AJ. Management of Trauma: Pitfalls and Practice, 2nd ed., Williams & Wilkins, 1996
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1. Which suture is best to ligate the cystic duct during a cholecystectomy? a. Nylon 3-0 b. Silk 2-0 c. Polyglactin 2-0 d. Cotton 4-0 e. Chromic 2-0
2. After insertion of a T-tube, repair of the CBD around the tube
is best with which suture? a. Silk 4-0 interrupted b. Cotton 4-0 continuous
c. Polyglactin 4-0 simple, interrupted d. Polypropylene 5-0 simple, interrupted e. Polyglycolic acid 3-0 continuous
3. The use of absorbable sutures is advocated when applying sutures in the biliary tree because?
a. It evokes less inflammation than non-absorbable sutures does
b. Non-absorbable sutures become nidus for later stone formation
c. Strictures are less common with the use of absorbable sutures
d. Leaks are less likely to occur with absorbable sutures e. Absorbable sutures are easier to handle
4. During a retrograde appendectomy, ligature of the base is performed using which suture?
a. Silk 2-0
b. Polypropylene 2-0 c. Polyglactin 3-0 d. Chromic 2-0 e. Polyester 2-0
5. The following suture materials may be used in closing the inner layer of a two-layer inverting bowel anastomosis, except:
a. Chromic catgut b. Polyglycolic